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Re: Lack of Running Giant Theropod Tracks

On 11/28/2010 6:44 PM, Sim Koning wrote:

Here I was focusing on the high probability that Triceratops was the one of the 
largest, most powerful and dangerous animals in its ecosystem *and* it may have 
been quite fast.


OK, trikes were problematic gut-pokers. We agree there.


I'm guessing that you were intentionally exaggerating with the boy scout 
comment, since some large sauropods would have been able swallow animals the 
size of a human child whole,
Not really. A gutsy young lad from (e.g.) Wyoming could do in a brachiosaurus in if he could get a bull rope on him in the right spot -- there were portions of the neck that were inaccessible to the sauropod. It would seem that finding a convenient tree to scrape the kid off with might work. But not if that trusty Randall knife was really sharp. No time.
How far would a severed sauropod artery spurt blood? How many liters per heart beat? 


and may have done so occasionally in order to increase the amount of calcium 
and essential amino acids in their diet.
Here is an example of said behavior: http://www.youtube.com/watch?v=saOOn2G16gE
And here is a perfect chance to mention a pet "could-have-done" I never saw mentioned anywhere else -- any sauropod that went into water regularly was undoubtedly presented with temptingly immobilized silt-stunned fish. A line of sauropods could have harvested large areas by silting up the water column and reducing O2 levels... *could have*. 


Again, I assume you mean sauropods. I am flabbergasted every time this
comes up on list, and I mean nothing personal in this. Everybody seems
to agree w/ you, but can offer nothing to defend this intuition become
an institution.


No, not specifically, since ceratopsids, giant ornithopods and ankylosaurs are 
not sauropods. You are either intentionally or unintentionally forming a straw 
man version of my argument.


Sorry.

I did that, but it was unintentional.
Given that T. rex was the only mega-theropod (afaik) that might *not* have had "the sauropod option", and also lived late in the dinosaur-ian era, I did not see any reason to exclude sauropods -- especially when how they both evolved to what they were is at the root of all these debates. So I jumped to a conclusion... 


Try a thought experiment -- drop down on all fours and become a
sauropod. Your neck is now as long as your torso, and as big around as
your finger, or maybe something a little more sensitive. How big is your
head? Really, really, small...


I would rather look at the actual animals and compare them with living analogs.
There are none, unless you count the relatively tiny giraffes. Even there, where is the tall biped w/ neck-encompassing jaws? We have to stick with the morphological realities the geo-record gives us. 


To start with, you are greatly exaggerating how small these animals heads were: 
they may seem rather small relative to their body size, but in absolute terms 
they were quite large. As an example, the skull of the Brachiosaur in Chicago 
is large enough for me to fit my head and shoulders into and I'm nearly 6 feet 
tall.


No. Relative to mega-theropod jaws, their heads and necks were tiny.


On ground where it's mobility is not impaired, any small and aggressive
dog could kill you easily with one bite should it be able to teach your
neck, even at the base.


I do not weigh 35 tons or more, and I do not have neck ribs protecting my 
throat and my carotid arteries. Also does your thought experiment allow me to 
rear up on my knees and smash the small dog with my fists? When you consider 
that giraffes use their head and necks as *weapons* the necks of sauropods may 
have been nearly as dangerous as their tails.


You guys who believe in the Zeus-like enraged sauropod should read --
"Proc. R. Soc. B -- doi:10.1098/rspb.2010.0898" aka "Scaling of sensorimotor control in terrestrial mammals -- Heather L. More1, John R. Hutchinson2, David F. Collins3, Douglas J. Weber4, Steven K. H. Aung5 and J. Maxwell Donelan1".
My take -- unless dino nerves were really special, the really big guys were, in fact, really really slow. 

"Dogs" are not slow, _when on good footing_.
To abandon the dog analogy -- a biped in deep mud would be in deep doodoo. The binary implications of substrate type cannot be ignored or overstated when assessing the respective capabilities of sauropods and theropods, or cataloging possible ecological scenarios. Anyplace a biped is very likely to fall, advantage sauropod. Anyplace the theropod can dodge and circle at will, advantage 100% theropod. 


Predators do not need to eat very often, and extremely large herbivores
do. How long do you think you can "rear up and thrash your tail"? Who
gets tired first? Are there trees or rocks? Well, then forget about
doing any tail-thrashing...


You are begging the question by assuming that sauropods would have been 
extremely slow and almost helpless.
I do assume they were relatively slow -- as in the slowest ever. I also assume they could and did get tired and de-hydrated. Anyother assumptions are special pleading when assessing the respective capabilities -- as is the old "they were just so big the theropods would be terrified" behavioral argument. 


You are also assuming that the risk of being trampled on by 50 ton animal and 
being struck by a swinging neck/tail would be low enough to make the attack 
worthwhile for a large theropod. There is no reason to presuppose either of 
these things since giraffes and elephants are both more than capable of killing 
lions and other large predators.
There are no extant analogues. Lions are not tall enough to reach giraffe necks, and elephants do not have spinal cords, major arteries, and brains in their trunks. Taking the theropod's perspective, I repeat -- on certain footing, the risk was minimal. In water/mud deeper than the theropod could stand, but shallow enough to give the sauropod footing, the risk was suicidal.
Old story -- S Douglas (very short, but an excellent marksman): "I challenge you to a duel." Abe Lincoln (tall, an awful marksman): "OK. Pole axes in 6 feet of water." Douglas: "@#$! $%! %!!!!" 


Imagine how easy an elephant would to kill if all you had to do was bite
the end of it's trunk. Think about it.



That's a fallacious argument because it's based on a false analogy: saurpods 
necks and elephant trunks are only similar in that they are elongated...that's 
it; some macronarians had heads large enough for them to actually bite back!
No, it isn't. Sauropod necks were mostly air, blood pressure extremely high, and very long. A 3 or 4 ton load on a 10 meter lever, and the most benign attachment points are mere centimeters away from nerve, muscle, vessel, maybe brain -- one crunch, game over. 


Tactically speaking -- a sauropod in a parking lot would be easy meat to
a persistent giant theropod.


If sauropods were as helpless as you seem to think they never would have evolved in the first 
place. Predators do not have some sort of "conservation" instinct: predators such as 
wolves will slaughter entire herds of sheep if they are helpless and can not get away. I have a 
feeling the same would have happened to sauropods if they were such "easy meat".
I disagree. Their vulnerability is why they were what they were -- they had to get the base of those necks as high as they could. Even so, relative to the tactical implications of the respective morphologies, they were helpless on flat ground, unless they could get to refuge. See below.
The other half of the coin must not be ignored -- a sauropod in a swamp or other place of uncertain footing, with deep footprints and knocked down trees inter-laced everywhere, was nearly as safe from the bipedal theropods as we are today :D... 


That or it could simply be because sauropods went extinct for whatever reason 
in North America and a species of titanosaurid migrated from another continent 
via a land bridge or an island chain. The formations that they are found in 
also span nearly 10 million years. Is there any evidence of Alamosaurus 
increasing in size along with the tyrannosaurids?
Could be. Actually, didn't the allosaurids and the sauropods disappear for N America at approximately the same time? 


I've read two of Hutchinson's papers so far and I found them very interesting, but I think the 
media (and most people in general) seem to think that studies or experiments equal 
"proof". The reality is there is no such thing as "proof" in science (outside 
of mathematics), only evidence. I imagine John Hutchinson would be the first to tell you that there 
are a *lot* of unknowns when forming computer models of an animal that has been dead for 65 million 
years. That being said, 25 mph isn't exactly walking, it's actually pretty fast. I would be 
interested to see how models would turn out if they included highly elastic tendons somewhat like 
those seen in macropods (kangaroos), which seem to hold up well under increased weight. I'm sure 
that was factored in to some degree since most or all tendons and muscles can work like springs. 
I'm also stumped as to how a 100 ton sauropod could support its weight if a tyrannosaur had just 
enough strength in its legs to walk quickly (10-15

mph) and not run.
Heh. I doubt JR Hutchinson would ever say "We know it all, I am going to retire now."
As to the rest -- there is a big difference between bipeds and quadrupeds in terms of what an engineer can do design-wise. 

And 25 mpg is fast. Too fast, imo.
People make a big deal of risk-avoidance by predators -- "Hmmm -- should I run 25 mpg on rough ground after something with horns everytime I get hungry, or should I crunch one skinny neck and feed the whole family for a week. Choices, choices..."
Seems simple to me, when viewed from a combined ecological and "opposing capabilities" perspective.
The biggest herbivore ever can be killed with one bite, and the null is that the species we know were ideally suited to bite them in that deadly spot were too scared to do it? Sorry, I do not buy it.
PERHAPS the very largest adults of the very largest species would have been marginally safe out in the 'parking lot' - but I doubt even that, unless it is true that the mega-theropods were big chickens. 

Golden eagle-type aggressiveness was more likely, in my view.